Prostate cancer is the most common form of cancer in men and the second leading cause of cancer deaths in men in the United States. The growth of prostate cancer is initially androgen dependent. Androgen ablation, the main therapy for prostate cancer, causes regression of androgen-dependent cancers. However, many men eventually die of recurrent, androgen-independent prostate cancer, a lethal form that inevitably progresses and metastasizes. However, the basic mechanism that determines the progression of prostate cancer is lacking. Recently several reports suggest that the change in mtDNA is associated with cancer progression, however, mechanisms has not been established yet. The overall goal of our research is to regulate or protect progression of prostate cancer by demonstrating and understanding the roles of mitochondrial DNA (mtDNA) on prostate cancer progression. During the previous grant period, we used several prostate cancer cell lines, mtDNA deficient cells, cybrids with nuclear DNA from mtDNA-deficient cells with normal mtDNA and tissue samples from prostate cancer specimens and demonstrated the critical roles of mtDNA content on prostate cancer progression. We also showed that Ras pathway is a key sequence for prostate cancer progression starting from reduction of mtDNA content. We also found the link from mtDNA reduction to ras activation. In specific aim 1a, we will investigate the link between reduction of mtDNA to Ras activation. In specific aim 2, we will further investigate the mechanistic link between reduction of mtDNA content to Ras activation followed by hormone refractory changes. In specific aim 3, we will investigate the connection of mtDNA to Ras activation for hormone refractory changes using in vivo mouse xenograft model. In this application, we will further investigate the roles of Ras pathway. An understanding of the mechanisms contributing to the development of androgen-independent and progressed phenotype in prostate cancer is currently lacking. This critical step accounts for the majority of the morbidity and mortality of this disease. Our novel hypothesis and preliminary/progressed report implicates mtDNA in the development of androgen-independence and prostate cancer progression. A confirmation of our hypothesis and an understanding of the underlying mechanisms could lead to novel approaches for prevention or therapy of prostate cancer.